@GiacomoC can you confirm that you were following the instructions provided on the Community Accounts FAQ page: 

How do I update the primary email address for my account?

1. Log in to accounts.pega.com
2. Hover on your name in the upper-right corner and select My Account Settings.
3. In the New Email Address field, enter your email address and click Send Verification.
4. You will receive an email to verify the new email account.
5. Once verified, return to My Account Settings and click the ellipsis (…) next to the email address you added above, and select Make Primary. Note: If needed you may remove other accounts by clicking Remove.                                                                                                                                                                                If you have any issues, contact [email protected]

What are the symptoms you experience?  We are not aware of any browser restrictions.  This must be a problem at your end.  Please clarify the troubleshooting you have carried out.

I was able to log into the Account Settings  using Chrome and add a new email address in the field.

Please check your browser tracer debug output to see if there are any js errors.

Please us the 'Contact us' links in the article if you require further help from our Accounts team.